I just picked up a s4 tii rx7 and have been away from stock rotaries for awhile. This car was said to be a pineapple rebuild about 15k ago. It seems to have misses at idle, exhaust leak, no to very low boost, and hard to no start when hot.

What I have found so far and will be getting fixed is the boost/pressure sensor nipple broken off, so it doesn't have a vac/boost source. A recent installed s5 manifold so the gasket is probably bad. Found the coolant sensor that is on the back of the water pump is broken so not plugged in.

That would pretty much cause those problems right?

 

Fix what you know is wrong with it and go from there.

It sounds like you're concerned with some more serious problems...compression check it if you're that worried.

 

Don't drive the car until you get at least the boost sensor fixed. The ECU uses both the AFM air volume and MAP data to determine fuel and timing. It'll run lean, and have improper timing under boost. A lack of a coolant temp sensor will also affect driveablity, so a new one will help.